Die cushion arrangement for presses



Oct. 12, 1954 w. ERNST 2,691,354

DIE CUSHION ARRANGEMENT FOR PRESSES Original Filed Sept. 15, 1949 4 Shets-Sheet 1 INVENTOR WALTER ERNST y Smsumm ATTORNEYS Oct. 12, 1954 w. ERNST DIE CUSHION ARRANGEMENT FOR PRESSES 4 Sheets-Sheet 2 Original Filed Sept. 15, 1949 HQ 2' INVENTOR WALTER ERNST ATTORNEYS Oct. 12, 1954 w. ERNST DIE CUSHION ARRANGEMENT FOR PRESSES 4 Sheets-Sheet 3 Original Filed Sept. 15, 1949 FIG. 3

INVENTOR WWW N W Emu R m m U T w A a FIG. 5

Oct. 12, 1954 w. ERNST 2,691,354

DIE CUSHION ARRANGEMENT FOR PRESSES Original Filed Sept. 15, 1949 4 Sheets-Sheet 4 Ziiw m. o

INVENTOR u. 1 WALTER ERNST By JW ATTORNEYS Patented Oct. 12, 1954 2,691,354 DIE CUSHION ARRANGEMENT FOR PRESSES Walter Ernst, Dayton, Ohio, assignor to The Commonwealth Engineering Company of Ohio, Dayton, Ohio, a corporation of Ohio Original application Se No. 115,901. Divided vember 2, 1950, Serial Claims. 1

This invention relates to presses and to die cushion arrangements therefor and is a division of my copending application Serial Number 115,- 901, filed September 15, 1949, and assigned to the same assignee as the instant application.

Die cushion arrangements are often employed in connection with presses, both mechanical and hydraulic, especially where a workpiece is to be drawn. A die cushion is useful in such circumstances in that it forms a resilient support for the article being drawn that prevents it from becoming torn or wrinkled as the drawing proceeds.

A die cushion thus constitutes generally a platen or a plunger to which a platen can be attached, and some arrangement for resisting movement of the platen or plunger so that a predetermined cushioning force can be exerted on the work member during the drawing operation.

Die cushions of this nature are also useful as ejectors for assisting in removing the workpiece after it has been drawn, and when functioning in this manner, may either follow the forming tool upwardly as it retracts after a drawing operation, or may move upwardly to eject the workpiece after the drawing tool has been retracted.

Ordinarily, die cushions of the type referred to are integrally associated with the press with which they are to be used at the time the press is manufactured, and thus form a permanent and inseparable part of the press. This is particularly true where the press is of any substantial size, say from five hundred tons to twenty-five hundred tons capacity.

It has been customary in the past in connection with presses of this type to order a press having a die cushion with the thought in mind that the principal utility of the press would be for drawing workpieces. Inasmuch as a die cushion, particularly one of the larger size, is an expensive auxiliary, presses having die cushions were substantially more expensive than ordinary presses. Accordingly, when a die cushion press of this nature was utilized for other work operations which did not require a die cushion, a much more expensive tool was being used than the job justified.

With a die cushion mounted integrally in a press frame, or so mounted as to be diflicult to remove, the utility of the press was further limited in that the space occupied by the die cushion was not available for any useful purpose.

The instant invention proposes an arrangement for a die cushion in a press such that the die cushion can be readily added to the press or readily removed from the press at any time in order to convert the press from standard to die cushion operation at will.

ptember 15, 1949, Serial an (1 this application No- The die cushion, readily detachable from the press, can be offered for sale as a separate item,

and only purchased when the job requirements justify it. Furthermore, the die cushion can readily be removed from the press and transferred to another if desired, and in this manner effect a substantial saving in the amount of investment necessary in order to provide a range of press capacities for various jobs.

This invention also provides improved control means for a die cushion of the nature referred to, whereby the die cushion can selectively oper ate on a plurality of diiferent types of cycles, such as the one where it immediately follows the drawing tool upwardly and the one where the upward movement of the die cushion is delayed until after the drawing tool has retracted.

The advantages referred to above, as Well as other advantages will become more apparent upon reference to the following description, taken in connection with the accompanying drawings, in which:

Figure l is a front elevational view of a hydraulic press embodying the die cushion structure according to my invention;

Figure 2 is a vertical section through the lower part of the press showing somewhat more in detail the construction of the die cushion;

I Figure 3 is a plan section indicated by line 33 on Figure 2;

Figure 4 is a plan section indicated by line 4-4 on Figure 2;

Figure 5 is a view indicated by line 5-5 on Figure 2;

Figure 6 is a view similar to Figure 5 but showing a somewhat modified arrangement of the die cushion of this invention; and

Figure 7 is a fragmentary view showing one of the valves forming a part of the operating circuit for the die cushion.

Referring to the drawings somewhat more in detail, the press shown in Figure 1 comprises the usual head l0 and bed I2, spaced apart by the uprights I 4, which enclose strain rods IS having the nuts it which retain the head, bed, and uprights clamped together.

The uprights serve to guide a platen 20 that may be powered by a ram 22 extending into the press head where it is connected with a double acting piston that can be acted on by fluid pressure to move the platen toward or away from bed I2.

A blankholder platen may be suspended from main platen 2t, as by rods 25, and is adapted for actuation by rods 28 which extend into the bed for connection to beams 29 that have thereon the pistons 30 in the cylinders 32. Cylinders 32 are fixed in bed l2 and are adapted for receiving fluid pressure via the flexible conduits 34 in the manner more fully disclosed in my application Serial Number 11590 1, identified above.

The .presszbed I2 is preferably a cast member and includes a substantially rectangular center opening 3t, as will be best seen in Figures 2,3, and 4. This central opening ,is utilized for receiving the die cushion or ejector unit according to this invention.

One type of die cushion unit. is illustrated in Figure 2, and comprises a single acting :plunger connected to the die cushion platen. .Thisdie cushion is adapted for relatively .lightservice; as when the press is equipped with a hlankholder.

A somewhat different die cushion arrangement is illustrated in Figure 6, wherein the die cushion platen is connected with a double acting plunger.

'This-diecushion is adapted for somewhat heavier "service and may be employed when apress is'not equipped with a .blankholder, but instead utilizes a draw'ring in association with the drawing die to obtain a blankholder action. The difierence between the two die cushion arrangements is, therefore, one of. degree and not of kind.

"For detachably receiving the-die cushion or ejector assembly, the press bed has the upstanding bored bosses 38 through which the strain rods :40 can'be passed for supporting the beams thatextendfrom the front to the back of the press and on the underneath side of the bed. "These beams are adapted for-receiving the projecting parts M of the die cushion or ejector cylinder 48 which reciprocably receives a plunger 50 on the upper end of which is'mounted a platen F 52. -"Platen 512 is adapted for being guided in its reciprocatory movements by the guide rails 54 mounted on the faces of ribsabout the cavity 36.

'It will be understood that usually there is' a bolster (plate resting on the upper surfaceof the -.press bed and that the platen'52 will normally bottom against the underneath side of the said bolster plate. In the manufacture of the press, the press bed is always formed with the rectangular-opening 36 extending therethrough and with the upstanding bored bosses 38, so that atany time it is desired to do so, thedie cushion or ejector assembly can be mounted in the press or removed therefrom. "The "illustrated arrangement permits this to be done in aminimum of time and at-a-minimum of expense. The die cushion assembly is removed simply by disconnecting the hydraulic lines thereto, taking the nuts olf one end of the strain rodsflfi, and lowering the assembly into a pit beneath the press. The die cushion arrangement of Figure 2 and that of Figure 6 have in common the feature of a check valve connected with the cylinder to raise the die cushion platen. In each case, the

check valve is icy-passed by a relief valve opening away from the cylinder so the die cushion platen will yield at a predetermined thrust and means are provided for locking the check valve closed to delay the upward movement of the die cushion platen, if so desired.

In Figure 2, the die cushion ram is single acting in its cylinder, whereas in Figure 6, the die cushion plunger 50 is double acting by means of a-pistcn 56 which closely fits in bore '58 of the die cushion cylinder 48.

The upper and lower ends of bore 58 are interconnected by passage 80 which has therein the check valve 62 adjacent the lower end of the cylinder and which is "by-passed by relief valve .-,mences. to -.move upwardly, .to flange fitting B8 to pass therefrom to the pushpassage duitiis.

, ment: shown iii-Figures 6 and 7. 52 normallyryields to pressure :standing on its .rtionary byan auxiliary :ed :for ibeingmoved upwardly against the bottom of the check valve member --ed thereto through-conduit .12. connected with conduit -65" through a three-way valve, 14' that also. includes, an exhaust line 16 and armovable. valve member 18.

' through relief valve Sland this :generates the required-pressure action upwardly on :the piston.

Part of the fluid displaced from the lower end of bore 58 passes to the upper end thereof through 60, and the remainder passes through conduit 66 to the flange fitting 68 mounted on the side of thepress, head and which is connected to the push-back side of the press plunger 22.

When=the pressing operation of the press is complete and the main platen of the press compressure is supplied back side of the press plunger '22 and into con- At this time the die cushion platen 52 may follow the main press platen upwardly or :may be, delayed .in its return.

' This 'isiaccomplished by the valving arrange- The check valve upper faceinpassage 5%), but may be held.- stapiston 18 which is adaptby pressure conduct- Conduita'lz is Valvemember i8'is normallylurged by a spring :80 .intor position to connectthe lower. branch of conduit 12 leading :isolenoid S2 by closure of limit; '.a cam- 82 on the press platenrZEl-will move valve -:member -18 into the position shown, wherein conduit .1 2' establishes a continuous passage-from gauxilia-ry .piston lildto-iconduit 166- With the valve member so shifted,

to auxiliary piston 10 with switch LS2 by the pressure supply .to thepushback side of the press plunger 22 to raise the press platen will also act on auxiliary piston 'lll and' clamp check valve 62 closed,.thereby pre- Wenting upward-movement of the .die cushion :platen.

*Whenthe press platen has moved farenough torelease limit switch .LS2,--so1enoid S2. is de- --energ-ized,- spring as is again, effective to. connect other-branch of conduit -12 leading .to' auxiliary Qthrust vis exerted thereon to cushion action.

' unit, isthesamount .of ..fluid piston l0 vwith exhaust conduit 1 iii-and check .walve -62. is then freeto open ,under'the pressure in passage on and to bring about .upward move- Umentvofr the die cushion plunger and platen.

It -is to be. noted thattheldie-cushion plunger {strand pistonlifi are so designed that .thecrossisectionalarea of plunger 58 is sufficient to bring about upward movement of the plunger and platenwhencheckvalve 6'2 is-open, and that piston'ifi is:.of such a. sizethat thenecessary give. the proper :die

Then, bymeans .of the interconnecting passage .60, the..only fluidthat itis ever necessary to supply to the .die

cushion unit through the conduit 6B, or to convey away from the die cushion displacedby the iplungerili as. it reciprocates in thecylinder48.

,A relatively small conduit can beutilized for conveying this amount .of fluid and. the arrangement represents a definite economyof piping.

Operation In operation the,press is operated by reciprocating themain platen 2|).by a reversible supply .plunger 22 du'it 12. up and the supply of fluid to the pushback side ing understood that the press could operate on manual cycle, semi-automatic, or full-automatic,

as desired.

if the press is to be operated with the die cushion, die cushion action is had when the'work is engaged by the platen and moved downwardly so as to move die cushion platen 52 downwardly.

When the die cushion platen is so moved, the accompanying downward movement of plunger 50 and piston 56 is resisted by the setting of relief valve 64.

Prior to the completion of the pressing stroke,

, cam 82 on platen 2s actuates switch LS2, thereby energizing S2 and moving valve member 18 into position to connect conduit 56 with con Then, when the press platen starts of the press ram is conveyed through conduit 55 to passage 60, it is also conveyed through conduit 12 to auxiliary piston 70 which moves upwardly and clamps check valve 62 closed. This prevents upward movement of the die cushionpiston, ram, and platen.

However, when cam 82 runs ofi switch LS2, valve member 18 shifts to exhaust conduit '52 thereby releasing auxiliary piston Ill and check valve member 62 so that pressure in passage 60 can act on both faces of piston 56 and urge it upwardly together with plunger 50 and die cushion platen 52.

The valve 14 may, of course, be made inoperative by opening switch 90, so that die cushion platen 12 will follow the main platen upwardly immediately, if so desired.

From the foregoing, it will be seen that the press of this invention can be a simple assembly consisting of the press frame with the main press platen and the actuating mechanism therefor, or that the same press can be equipped with a die cushion and operate as a die cushion press for carrying out certain types of work.

The addition of the die cushion does not require the addition of any more hydraulic horsepower and imposes no load on the press frame except a certain amount of mechanical loading on the bottom of the bed which in no way detracts from the structural strength of the press frame,

because this portion of the frame is never loaded to a critical degree during operation of the press.

It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions, and, accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

I claim:

1. In a hydraulic press having a main platen and a die cushion platen; said main platen having fluid operable advancing and retracting means, a double acting plunger having its rod end connected with said die cushion platen, a cylinder in which said plunger is reciprocable, a passage in the cylinder connecting the opposite ends thereof, a check valve in said passage having its inlet toward the rod end of said cylinder and its outlet toward the other end of said cylinder, a relief valve bypassing said check valve and responsive to a predetermined pressure at said outlet for permitting fluid to flow from the outlet to the inlet thereof, means hydraulically connecting the inlet of said check valve with said fluid operable retracting means for the said 6 main platen for fluid flow therebetwe'en in both directions, a clamping piston associated with'said check valve responsive to fluid pressure for clamping said check valve in its closed position, said piston having a greater effective area than the area of the checkvalve that is exposed to the pressure at the inlet thereof when the check valve is closed, and means for selectively connecting said piston with said fluid operable retracting means for holding said plunger stationary during a supply of pressure to said fluid operable retracting means.

2. An arrangement as set forth in claim 1 in which the last-mentioned means comprises a valve between said "piston and said fluid operable retracting means normally positioned for connecting said piston with exhaust, electrical means energizable for shifting said valvet'o connect said piston with said fluid operable retracting means, a switch for energizing said electrical means, and a cam carried by said main platen operable for engaging and closing said switchwhen the main platen is adjacent its fully advanced position.

3. In a die cushion arrangement of the type described; a cylinder, a plunger extending into said cylinder, relief valve means connected with said cylinder for resisting the discharge of fluid therefrom thereby to resist movement of the plunger into said cylinder, a supply of pressure fluid, a check valve connecting said supply with said cylinder and opening toward the cylinder, said check valve comprising a valve body having a bore, a check valve member reciprocable in said bore from a seated position where the bore is closed to a position where the bore is open for the passage of fluid, said valve member when seated presenting a predetermined area to pressure fluid supplied to the inlet of the valve, an auxiliary piston in said bore on the opposite side of said valve member from the seat of the valve, and means selectively operable for supplying pressure fluid to the side of said piston opposite said valve member for clamping said valve member in its seated position, said piston having an area greater than said predetermined area of the valve member whereby a supply of fluid at any pressure to both the inlet of the check valve and the auxiliary piston will clamp the valve closed.

4. In a die cushion arrangement of the type described; a cylinder, a plunger extending into said cylinder, relief valve means connected with said cylinder for resisting the discharge of fluid therefrom thereby to resist movement of the plunger into said cylinder, a supply of pressure fluid, a check valve connecting said supply with said cylinder and opening toward the cylinder, said check valve comprising a valve body having a bore, a check valve member reciprocable in said bore from a seated position where the bore is closed to a position where the bore is open for the passage of fluid, said valve member in seated position presenting a predetermined area to pressure fluid delivered to the inlet of the valve, an auxiliary piston in said bore on the side of said valve member toward which the valve member moves toward bore opening position, said piston having a greater area than said predetermined area of said valve member, means normally connecting the bore on the side of the piston opposite said valve member with exhaust, and means selectively operable for connecting the said side of the piston with the inlet side of said check valve whereby the supply of pressure fluid to the said inlet will cause said auxiliary piston to -clamp the valve member initsrbore closingcpoends thereof, a check valve in said passage having its inlet toward the rod end of said cylinder and its outlet toward the other endofsaid cylinder, means associated withvsaid check valve responsive to a predetermined-pressure atltheoutlet thereof for permitting ,fiuid ,ltofinw fromthe 1 outlet to theinlet thereof when said plunger moves during a working stroke .oisaid main .platen, means hydraulically connecting the inlet of said check valve with said fluid operable retracting means for the said main platen for theexchange of fiuidtherebetweenin both directions so that, normally, saidv check valve. will be opened by the. pressure fluid supplied to said fluid operable retracting means for the .main platen whereby said plunger will be urged, upwardly upon a supply of pressure, fluid to said fluid operable retracting means simultaneously with the upward, travel of the maineplaten. fluid actuated means associated with said checkyalve responsive to fluid pressure for preventingppen- 'ing of said check valve for holding-said plunger stationary when the main platen retracts .upona supply of pressure fluid to said fluid operable, retracting'means, and means selectively operable for supplying pressure fluid to the-said fluid actuated means associated with saidcheck-valve during the initial retracting movement of said platen.

References Cited in the file. of this patent UNITED STATES PATENTS Number Name Date 1,354,785 Strand Oct. 5, 1920 1,483,204 Strand Feb. 12, 1924 1,670,552 Rode May 22,. 1928 1,706,075 Rode Mar. 19, 1929 1,849,691 Rode Mar. 15,.1932 1,861,337 Ernst May 31,1932 2,380,153 Davis July .10, 1945 2,382,046 Flowers at al Aug. 14,- 1945 2,396,296 Stacy -Mar. 12, 1946 2,441,539 Aldredge May 11, 1948 

